DIFFUSIVITY OF RARE EARTH ION IN POROUS ION EXCHANGE RESINS

TheporousionexchangeresinshavebecomeanimportantreactivepolarermaterialwhicharewidelyappliedinindustrialoperationsHowever,afewstudi..[l--3]reportedtheintraparticlediffusivityofporousionexchangers.Theionexchangedisplacementprocessonporousresinbedforseparationofrareearthsistheoneofthebestwaystoenhancetheeffectivityofthismethod.TounderstandthediffusionoftheionintheresinisveryavailablefolimproVingtheprocess.EXPERIMENTAL1.Pre--experimentsAllthereagentsusedareA.R.grade.152'154Euisusedasaradiot…     

Enthalpies of Dilution and Enthalpies of Mixing of Amino Acids with Sucrose in Aqueous Solutions at 298.15 K

The enthalpies of mixing of aqueous solutions have been determined for sucrose with six different amino acids (glycine, l-alanine, l-serine, l-valine, l-proline and l-threonine) at 298.15 K, by using a LKB-2277 flow microcalorimetric system. These results, along with the enthalpies of dilution of these solutes for the initial solutions, were used to determine the enthalpic interaction coefficients (h _xy, h _xyy, h _xxy) of the McMillan–Mayer Theory. The pair-wise cross interaction coefficients of amino acids and sucrose are discussed from the viewpoint of solute–solute interactions.     

Aqueous solutions containing amino acids and peptides. Part 22 - free energetic and enthalpic virial coefficients at 25°C for some interactions of isofunctional amides

The excess free energies of aqueous solutions containing N-acetyl-L-prolinamide, N-acetyl-N-methyl-L-alaninamide and binary mixtures of these have been determined at 25°C from isopiestic measurements. The corresponding excess enthalpies for the last two systems have been obtained from enthalpy of dilution measurements. The results derived have been considered using the Savage-Wood group additivity principle, and it is shown that this works remarkably well although deviations are observed which are probably significant.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.     

Isotope exchange kinetics at heterogeneous solid surfaces (solid-liquid interfaces)

A system of equations describing isotope exchange kinetics at heterogeneous solid surfaces (solid-liquid interfaces) is studied numerically. The theoretical kinetic curves, characterizing the isotope exchange, are calculated for different discrete distributions of the isotope exchange rate constant.

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Isotopenaustauschkinetik an heterogenen Festkörperoberflächen (Fest-flüssig Grenzflächen)

Zusammenfassung Ein die Kinetik des Isotopenaustausches an heterogenen Festkörperflächen (fest-flüssig Grenzflächen) beschreibendes Gleichungssystem wird einer numerischen Auswertung unterzogen. Die theoretischen kinetischen Kurven des Isotopenaustausches werden für verschiedene diskontinuierliche Verteilungen der Isotopenaustausch-Geschwindigkeitskonstante berechnet.

     

Enthalpies of dilution of aqueous electrolytes: The NaCl/H2O system

Analysis of enthalpy of dilution data for the system NaCl/H₂O at 298.15°K with correlating equations presently in widespread use shows that these do not satisfactorily fit the data at the lowest available concentrations. A new approach based on the extended Debye-Hückel theory is suggested. It is shown that a plot of the ratio of the apparent molar enthalpy of dilution to the change in ionic strength, L/I, versus (I _i ^1/2 –I _f ^1/2 )/I, should give a straight line at low enough concentration with a slope 2S _H/3. The intercept is related to the Debye distance parameterA and the coefficient of the first virial correction term. The quantityS _H is the limiting Debye slope as calculated from the properties of the pure solvent. These expectations are substantiated by the fits. Values of the parameters are compared with older estimates, and it is concluded that the choiceA=0 is reasonable.     

盐卤硼酸盐化学——Ⅺ.不同含硼浓缩盐卤的稀释实验

前文[1]报道高含硼浓缩盐卤加水稀释过程中硼酸盐的行为。考虑到青海省柴达木盆地大柴旦盐湖卤水日晒蒸发到钾盐析出阶段,浓缩卤水中含1.87％MgB_4O_7,蒸发到水氯镁石开始析出,浓缩卤水中含2.95％MgB_4O_7。本文报道,这两种不同含硼浓缩卤水按文献[1]中实验步骤进行加水稀释,室温放置过程中析出硼酸镁盐的某些不同结果。     

The IRMM – International Measurement Evaluation Programme,IMEP

 The aim of the International Measurement Evaluation Programme (IMEP) is to give an objective picture of the state-of-the-practice (SoP) of chemical measurements in field laboratories by comparing them to a reference range that contains a value that is as traceable to the SI system of measurements (in this case to the Avogadro Constant, one of the best realizations of the mole so far), as can presently be achieved, but which in any case is independent of human or political decision. Thus, a large-scale field test has been made to realize (international) comparability of these measurements by providing them with an independent scientific common basis. In the third measurement round, IMEP-3, ten trace elements, B, Ca, Cd, Cu, Fe, K, Li, Pb, Rb and Zn were measured in a synthetic and in a natural water by about 155 participating laboratories using their routine methods. The (coded) results are graphically reported and compared to certified reference values, established by IRMM and NIST, using isotope specific methods (isotope dilution mass spectrometry and neutron activation analysis), wherever possible. One of these methods (IDMS) has recently been defined as a primary method of measurement by the Consultative Committee on Amount of Substance (Comité Consultatif pour la Quantité de Matière: CCQM) in its founding meeting in April 1995 at BIPM, Paris. Results indicate a spread of more than ±50%, asymmetrically distributed around the reference range, although the declared accuracy was 5–10%. Self-assessment by participants of their analytical capabilities does not show a high correlation between a self-rating ("more experienced" or "less experienced") and actual performance. In the way they have been applied, all methods seem to produce results of approximately the same quality. There is little reduction in the spread of the measurements if the results obtained for one element in the natural water B are divided by the results obtained for the same element in the synthetic water A (which was unknowingly, a reference material). Index entries International measurement evaluation programme (IMEP).     

Low temperature thermodynamic properties of Gd<Subscript>2</Subscript>SrCo<Subscript>2</Subscript>O<Subscript>7</Subscript>

Summary Thermodynamic properties of a layered perovskite oxide Gd₂SrCo₂O₇ have been studied. Powder X-ray diffraction, electric resistivity, magnetic susceptibility and heat capacity measurements were carried out. The crystal structure was determined as I4/mmm. The temperature dependence of the magnetic susceptibility was fitted to the Curie-Weiss behavior with antiferromagnetic interaction. Spin state of Co³⁺ ion was derived to be intermediate spin state configuration (t_2g⁵e_g¹). The spin ordering was observed as a broad anomaly in the heat capacity curve with a peak at 2 K. The measured entropy was 35.47 J K^-1mol^-1, which was 65% of expected value. Thus the spin ordering should not be completed at the lowest temperature 0.2 K covered in the present experiments and/or some short range ordering remains at higher temperatures.     

Enthalpic Interactions of Amino Acids with Glucose in Aqueous Solutions at 298.15 K

The enthalpies of mixing of aqueous glucose solutions and six kinds of aqueous amino acid solutions (glycine, L-alanine, L-serine, L-valine, L-proline, and L-threonine) and their respective enthalpies of dilution have been determined at 298.15 K using flow microcalorimetry. The experimental data have been analyzed in terms of the McMillan–Mayer model to obtain the heterotactic interaction coefficients. The results have been interpreted from the point of view of solute–solute interactions.     

Activity coefficient at infinite dilution, azeotropic data, excess enthalpies and solid–liquid-equilibria for binary systems of alkanes and aromatics with esters

Binary azeotropic data have been measured at different pressures for ethyl acetate + heptane, methyl acetate + heptane, isopropyl acetate + hexane and isopropyl acetate + heptane by means of a wire band column. Additionally activity coefficients at infinite dilution have been determined for ethyl acetate and isopropyl acetate in decane and dodecane in the temperature range between 303.15 and 333.15 K with the help of the dilutor technique. Furthermore excess enthalpies for the binary systems methyl acetate + hexane, methyl acetate + decane, ethyl acetate + hexane and ethyl acetate + decane at 363.15 and 413.15 K have been studied with the help of isothermal flow calorimetry. Finally solid–liquid equilibria for the systems ethyl myristate + benzene and ethyl myristate + p-xylene have been investigated by a visual technique. All these data have been used for the revision and extension of the group interaction parameters of the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR. The experimental data was compared with the results predicted using the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.